In GNU Emacs 31.0.50 (build 1, aarch64-apple-darwin24.5.0, NS appkit-2575.60 Version 15.5 (Build 24F74)) of 2025-05-13 built on pro2 The transient-posframe display changed which I bisected to 6017c6a986fd958732facb1bb6ea2c040981b023 is the first bad commit commit 6017c6a986fd958732facb1bb6ea2c040981b023 Author: Martin Rudalics Date: Mon Dec 23 10:59:11 2024 +0100 Make 'fit-frame-to-buffer' work around size hints (Bug#74866) * lisp/window.el (fit-frame-to-buffer-1): When 'frame-resize-pixelwise' is nil, round up requested sizes to avoid that lines get wrapped (Bug#74866). * doc/lispref/windows.texi (Resizing Windows): Mention that with size hints one may have to set 'frame-resize-pixelwise' to make 'fit-frame-to-buffer' fit the buffer exactly. doc/lispref/windows.texi | 4 +++- lisp/window.el | 20 ++++++++++++++++++++ 2 files changed, 23 insertions(+), 1 deletion(-) After that change, an additional line is displayed at the bottom of the child frame that transient-posframe uses to display a transient. Screen shot from the NS GUI on macOS: